Support mutation

angel_serialize_generator/example/main.g.dart

@@ -11,10 +11,10 @@ class Todo extends _Todo {
   Todo({this.text, this.completed});
 
   @override
-  final String text;
+  String text;
 
   @override
-  final bool completed;
+  bool completed;
 
   Todo copyWith({String text, bool completed}) {
     return Todo(

angel_serialize_generator/lib/model.dart

@@ -45,10 +45,15 @@ class JsonModelGenerator extends GeneratorForAnnotation<Serializable> {
         clazz.fields.add(Field((b) {
           b
             ..name = field.name
-            ..modifier = FieldModifier.final$
+            // ..modifier = FieldModifier.final$
             ..annotations.add(CodeExpression(Code('override')))
             ..type = convertTypeReference(field.type);
 
+          // Fields should only be forced-final if the original field has no setter.
+          if (field.setter == null && field is! ShimFieldImpl) {
+            b.modifier = FieldModifier.final$;
+          }
+
           for (var el in [field.getter, field]) {
             if (el?.documentationComment != null) {
               b.docs.addAll(el.documentationComment.split('\n'));

angel_serialize_generator/test/book_test.dart

@@ -41,6 +41,13 @@ main() {
           deathlyHallows.updatedAt.toIso8601String());
     });
 
+    test('can be mutated', () {
+      var b = deathlyHallows.copyWith();
+      b.author = 'Hey';
+      expect(b.author, 'Hey');
+      expect(b.toJson()[BookFields.author], 'Hey');
+    });
+
     test('heeds @Alias', () {
       expect(serializedDeathlyHallows['page_count'], deathlyHallows.pageCount);
       expect(serializedDeathlyHallows.keys, isNot(contains('pageCount')));

angel_serialize_generator/test/models/book.g.dart

@@ -23,32 +23,32 @@ class Book extends _Book {
       : this.notModels = List.unmodifiable(notModels ?? []);
 
   @override
-  final String id;
+  String id;
 
   @override
-  final String author;
+  String author;
 
   @override
-  final String title;
+  String title;
 
   @override
-  final String description;
+  String description;
 
   /// The number of pages the book has.
   @override
-  final int pageCount;
+  int pageCount;
 
   @override
-  final List<double> notModels;
+  List<double> notModels;
 
   @override
-  final String camelCaseString;
+  String camelCaseString;
 
   @override
-  final DateTime createdAt;
+  DateTime createdAt;
 
   @override
-  final DateTime updatedAt;
+  DateTime updatedAt;
 
   Book copyWith(
       {String id,
@@ -126,7 +126,7 @@ class Author extends _Author {
       : this.books = List.unmodifiable(books ?? []);
 
   @override
-  final String id;
+  String id;
 
   @override
   final String name;
@@ -148,10 +148,10 @@ class Author extends _Author {
   final String obscured;
 
   @override
-  final DateTime createdAt;
+  DateTime createdAt;
 
   @override
-  final DateTime updatedAt;
+  DateTime updatedAt;
 
   Author copyWith(
       {String id,
@@ -221,16 +221,16 @@ class Library extends _Library {
       : this.collection = Map.unmodifiable(collection ?? {});
 
   @override
-  final String id;
+  String id;
 
   @override
   final Map<String, _Book> collection;
 
   @override
-  final DateTime createdAt;
+  DateTime createdAt;
 
   @override
-  final DateTime updatedAt;
+  DateTime updatedAt;
 
   Library copyWith(
       {String id,
@@ -283,7 +283,7 @@ class Bookmark extends _Bookmark {
         super(book);
 
   @override
-  final String id;
+  String id;
 
   @override
   final List<int> history;
@@ -295,10 +295,10 @@ class Bookmark extends _Bookmark {
   final String comment;
 
   @override
-  final DateTime createdAt;
+  DateTime createdAt;
 
   @override
-  final DateTime updatedAt;
+  DateTime updatedAt;
 
   Bookmark copyWith(_Book book,
       {String id,

angel_serialize_generator/test/models/game_pad_button.g.dart

@@ -49,10 +49,10 @@ class Gamepad extends _Gamepad {
         this.dynamicMap = Map.unmodifiable(dynamicMap ?? {});
 
   @override
-  final List<_GamepadButton> buttons;
+  List<_GamepadButton> buttons;
 
   @override
-  final Map<String, dynamic> dynamicMap;
+  Map<String, dynamic> dynamicMap;
 
   Gamepad copyWith(
       {List<_GamepadButton> buttons, Map<String, dynamic> dynamicMap}) {